This invention relates to a separator assembly utilizing one or more hydrocyclones for use xe2x80x9cdownholexe2x80x9d in a hydrocarbon well for separating oil and water in a production flow from the subterranean hydrocarbon reservoir.
The use of hydrocyclones to separate oil and water from the production flow of an oil well is well known. It is also well known that hydrocyclones can be designed to operate as bulk oil/water separators which primarily are designed to separate oil from the production flow where the mixture contains a relatively high proportion of oil; pre-deoiler separators designed to separate oil from a flow where there is a lower concentration of oil, for e -ample the water and oil mixture discharged from a bulk oil/water separator; and, deoiler separators designed to operate on mixtures with a low concentration of oil in water, so as to be able to discharge substantially clean water back into the environment.
There is a significant energy wastage in transporting downhole water to a surface processing station for subsequent discharge back into the environment. Thus an objective of downhole separation is to remove water from the fluid which is transported to the surface and usually therefore downhole separation systems make use of bulk oil/water hydrocyclones, and pre-deoiler hydrocyclones.
There have been a number of prior proposals for downhole hydrocyclone separation systems. Generally such systems comprise an outer tubular structural housing dimensioned to fit closely within the fixed well casing of the oil well and providing a supporting structure for locating and securing a plurality of hydrocyclones therein. Complex piping within the housing communicates with the outlets of the hydrocyclones so that separated water can be reinjected back into the hydrocarbon reservoir by way of injection into a formation above or below the production zone, and an oil rich mixture resulting from the removal of some of the water can be transported to the surface. It has been suggested (see for example Norwegian Patent Application P962337) that the hydrocyclones may be supported by oil and water manifolds, but no mechanism for this has been disclosed.
The use of an outer cylindrical housing, containing the hydrocyclones and connecting piping, as the structural element of a separator assembly is disadvantageous in that the housing is, of necessity, a robust, large diameter component occupying a significant amount of the space available in the well casing and consequently restricting the production flow in the well casing with the attendant risk of shearing of the oil droplets in the production flow.
It is an objective of the present invention to provide a separator assembly, for use downhole, in which the aforementioned disadvantages are minimised.
In accordance with the present invention there is provided a separator assembly comprising an elongate body member including longitudinally extending oil and water passages, the elongate body member defining a longitudinally extending mounting face to which at least one hydrocyclone is secured, said hydrocyclone having its axis extending generally longitudinally of the elongate body, a first connecting union at the overflow end of the hydrocyclone whereby the overflow outlet of the hydrocyclone communicates with the oil passage of said body member, a second connecting union at the underflow end of the hydrocyclone whereby the underflow outlet of the hydrocyclone communicates with the water passage of said elongate body member, and, connecting means at opposite axial ends respectively of the elongate body member for establishing communication with said oil and water passages respectively.
Preferably said first and second connecting unions provide the means of securing the hydrocyclone to the elongate body member.
Preferably each elongate body member carries a plurality of hydrocyclones.
Preferably the or each hydrocyclone is disposed with its longitudinal axis inclined with respect to the longitudinal axis of the respective elongate body member.
Conveniently the elongate body member defines a generally transversely extending hydrocyclone mounting surface and said oil and water passages are disposed side-by-side with their axes in a plane generally parallel to the plane of said mounting surface, the spacing of the axes of said oil and water passages being so chosen in relation to the length and inclination of the hydrocyclones that said first and second connecting unions at opposite axial ends respectively of the hydrocyclone aligned with the respective oil and water passages.
Preferably the elongate body member includes a second water passage parallel to and spaced from the first water passage and the oil passage, said oil passage being disposed between said first and second water passages.
Conveniently first and second hydrocyclones are secured to the elongate body member with their longitudinal axes parallel to one another and inclined to the longitudinal axis of the body member, said hydrocyclones overlapping in side-by-side relationship and extending in opposite directions, the overflow outlets of the two hydrocyclones being aligned with one another lengthways of the body member so that their connecting unions communicate with the oil passage, while the connecting unions at the underflow ends of the two hydrocyclones communicate with the first and second water passages respectively.
Conveniently first and second hydrocyclones extending in opposite directions are secured to the elongate body with their longitudinal axes co-extensive, the hydrocyclones having their overflow outlets adjacent one another and communicating with a common connecting union connecting the two overflow outlets to the oil passage of the body.
Conveniently the axially aligned hydrocyclones have their co-extensive axes parallel to the axis of the elongate body.
Alternatively the axially aligned hydrocyclones have their co-extensive axes inclined with respect to the longitudinal axis of the elongate body such that the overflow outlets of the hydrocyclones communicate with the oil passage through said common connecting union, and the connecting unions at the underflow ends of the two hydrocyclones communicate respectively with the first and second water passages.
Preferably the elongate body member includes opposite axial end bosses of circular cylindrical form and said mounting surface of the elongate body is approximately diametric in relation to the cylindrical bosses.
Desirably the or each inlet of the or each hydrocyclone is an exposed inlet so as to accept liquid mixture flowing in the region of the mounting face of the elongate body.
Preferably where said hydrocyclones are configured to be bulk oil/water hydrocyclones the mounting surface of the elongate body member is exposed in use to the production flow within the well casing such that production flow enters the inlets of the hydrocyclones.
Alternatively where the hydrocyclones are configured to operate as pre-deoiler hydrocyclones then a cover member is sealingly engaged with the elongate body member to define with the mounting surface of the body member an inlet chamber which, in use, is flooded through an inlet passage with the underflow from bulk oil/water hydrocyclones.
The invention further resides in a downhole separator string comprising a plurality of separator assemblies as defined above interconnected with their elongate body members in end-to-end relationship.
Preferably the string includes pre-deoiler separator assemblies and bulk oil/water separator assemblies and the pre-deoiler separator assemblies are positioned lower in the string, in use, than the bulk oil/water separator assemblies, the underflow of the bulk oil/water separators passing down the string to the pre-deoiler separator assemblies, the underflow of which is disposed of by, for example, reinjection, the oil overflow of the pre-deoiler separators passing upwardly through the string to be mixed with the oil overflow of the bulk oil/water separators for transport to the surface.
Preferably the body member of each of the bulk oil/water separator assemblies includes an additional oil passage through which oil from pre-deoiler separator assemblies lower down the string is transported upwardly.
Conveniently said further oil passage is housed within the first mentioned oil passage of the elongate body member of the bulk oil/water separator assemblies.